Field of the Invention
The invention concerns a method and a configuration for driving an actuator, in particular a piezoelectrically operated fuel injection valve of an internal combustion engine.
Published, Non-Prosecuted German Patent Application DE 196 53 666 A1 discloses a method for quickly driving capacitive loads in which a control circuit is controlled by a control device. In this method, the interaction of an upward and downward controller in the control circuit and an evaluation of a load voltage and load current values together with a fast digital controller make it possible to produce to a great extent any desired voltage characteristics at the capacitive load.
Published, Non-Prosecuted German Patent Application DE 196 52 807 A1 discloses transferring predeterminable energy to an actuator by transferring the charge of a charging capacitor partially to the actuator via a ring-around coil. A deviation in the metered amount of energy supplied in a driving operation is established on the basis of a family of characteristic maps or fields and is corrected incrementally in the next driving operations. The family of characteristic maps are determined experimentally from the predetermined component values of the configuration and the temperature-dependent actuator capacitance.
This method of driving an actuator presupposes that the capacitance of the charging capacitor and the inductance of the ring-around coil are precisely known. However, coils and capacitors usually have production-related tolerances of approximately .+-.10%; in addition, their values change during operation in dependence on temperature and aging. By measuring an inductance and a capacitance at the end of the line, component tolerances can be detected and taken into account in the driving method. A further solution is to use components with low production tolerances, which however leads to high component prices. External influences during operation, such as temperature influences or aging of the components for example, are not taken into account in the two solutions.